As a pressure sensor of this type, there has been conventionally proposed a pressure sensor including a cap disposed on a substrate provided with a diaphragm (see Patent Literature 1, for example).
Specifically, in this pressure sensor, the substrate having a first surface and a second surface is provided, in the second surface, with a recess. The diaphragm is provided between the bottom surface of the recess and the first surface of the substrate. The diaphragm has a first surface provided with a plurality of gauge resistors so as to configure a bridge circuit. The cap is disposed on the first surface of the substrate such that the gauge resistors are sealed and a reference pressure chamber is provided between the cap and the first surface of the substrate.
When a measurement medium is introduced to the recess provided in the substrate of the pressure sensor thus configured, the diaphragm is deformed in accordance with differential pressure between pressure of the measurement medium and pressure in the reference pressure chamber. The gauge resistors provided on the diaphragm are deformed to cause variation in output voltage of the bridge circuit and cause output of a sensor signal according to the differential pressure.
However, in the pressure sensor, foreign matter in the measurement medium possibly adheres to a portion of the diaphragm exposed to the measurement medium. The foreign matter adhering to this portion reduces pressure applied to the diaphragm so as to be lower than actual pressure of the measurement medium. In other words, the foreign matter restrains deformation of the diaphragm. The pressure sensor thus has a problem that detection accuracy deteriorates if foreign matter adheres to the portion of the diaphragm exposed to the measurement medium.